Strain-relief bushing



July 29, 1947. F. KLUMPP, JR

STRAIN-RELIEF BUSHING Filed March 2, 194a FIG. 4

FIG. 3

FIG. 2

- INVFJVTOR. FERDINAND KLUMPP, in.

Patented July 29, 1947 STRAIN-RELIEF BUSHING Ferdinand Klumpp, Jr.,Union, N. J., assignor to Heyman Manufacturing Company, Kenilworth,

Application March 2, 1946, Serial No. 651,548

7 Claims.

This invention relates to a self-loclin strainrelief bushing that isadapted to securely lock and hold an electrical conductor or cable inthe bushing and to a mounting plate or support having a hole into whichthe bushing is inserted.

The principal object of my invention is to provide a self-lockingstrain-relief bushing which is automatically locked in place in the holein the plate or support by merely pushing the same into position afterplacing the bushing over the conductor or cable.

Another object or" my invention is to provide a strain-relief bushingwhich will positively lock the conductor or cable in the support platewhereby the conductor or cable is prevented from turning or being movedlongitudinally in the bushing and the bushing is prevented from turningin the plate or support member.

The improved features of my new strain-relief structure will be readilyunderstood and appreciated by reference to the annexed drawing wherein,

In all the figures the views are made on an enlarged scale from workingmodels.

In the drawing:

Figure l is a plan View of one of the parts of my two-piece bushing,looking at what I term the open or recess side.

Figure 2 is a side view of Figure 1.

Figure 3 is an end view of Figure 1 looking from left to right.

Figure 4 is a side View of the other part of the bushing.

Figure 5 is a top plan view of Figure 4.

Figure 6 is an end View of Figure 5 looking from left to right.

Figure '7 is a sectional view of the two parts in assembled position inthe mountin plate showing the manner in which the conductor or cable isgripped or held in position in the bushing.

Figure 8 is a plan view of one of the parts of a slightly modifiedconstruction looking at the interior of the part.

Figure 9 is a view similar to Figure 1 but of a part which is adapted tocooperate with the part shown in Figure 8.

Figure 10 is an end view of Figure 8 looking from right to left.

Figure 11 is an end view of Figure 9 locking from right to left.

In the various views wherein like numbers refer to corresponding parts,I is the body portion comprising one of the parts of the bushing. Thebody or part I has a flange 2 which is adapted to engage one side of amounting plate 3 having a hole therein to receive the bushing as shownin Figure '7. The body I has side fiat portions 4 and 5 to fit in acooperative hole in the mounting plate or support 3 so as to prevent thebushing from turning in the plate or support 3. The body I is providedwith a longitudinally extend ing channel 6 the bottom surface of thechannel is interrupted by a reecss 1 while the side walls having theouter flat sides 4 and 5 are provided with guide channels 8 and 9 whichare adapted to receive the other piece l3 of the bushing which may betermed a grip block having a downwardly extending portion H the sides [8and IQ of which are adapted to fit in and slide in the guide channels 8and 9. The end !4 of the grip block is is shaped to conform to and formpart of a holding flange. Rearwardly of the flange 2 on the member Ithere is an arcuate groove I9 and a corresponding groove IS in themember l3, these cooperative grooves being adapted to receive materialaround the hole in the mounting plate 3 as shown in Fi u e '7. T e partI has a portion II which forms the rear end of the longitudinal channel6. The portion i I has an arcuate tapered surface l2 and likewise thepart l3 has the tapered end I5, both tapered ends being for the purposeof ease in assembling the two-part bushing into the hole in the mountingplate 3. It will be noted in Figure 6 that the downwardly projectingportion IT has formed at its extremity arcuate surfaces 20 and 2!. Theseare for the purpose of engaging a twin conductor or cable C. It is to beunderstood that if a single conductor or cab-1e is used one arcuatesurface would take the place of the two shown in Figure 6. When thebushing is installed in a plate or support 3 as shown in Figure '7 itwill be seen that the two parts are forced toward each other and theprojection l1 engages the cable 0 pushing it downwardly into the recess1 in the part I thereby absolutely locking the cable or conductorsecurely in the bushing so that it cannot be turned therein or pulledlongitudinally.

In the modified forms shown in Figures 8 to 11 the part 22 correspondsto the part I of the structure shown in Figure 7. The part 22 has thesame recess '1 and guide channels 8 and 9, flange 2 and groove II! as inpart I. Likewise part 23 has a downwardl projecting part 24 havingarcuate recesses 26 and 2! the same as shown in Figure 6, and inaddition this piece also has a part of the longitudinal channel 6therein, the channel being intercepted however, by the projection 24while in the piece 22 the channel 6 is intercepted by the recess 1 as inFigure l. The

manner of gripping the cable by the parts shown in Figures 8 to 11inclusive is the same as shown in Figure 7.

While in Figures 8 to 11 inclusive I have illustrated and described thestrain-relief device as being made in two parts the downwardlyprojecting part 24 may be made as a separate piece, slidable into theguide channels 8 and 9. With this modification the two identical parts22 would be utilized together with the removable projection 24. Withthis construction only two moulds would be required as in Figure 1 sincethe two parts 22 would be identical. Also by reason of this latterconstruction the device is more readily adaptable for a single conductoras only the very small mould would be required for the part 24 having asingular arcuate surface for a single conductor, whereas in theconstruction shown in Figure 6 a more expensive mould would be requiredto make a complete new part.

From the preceding description it will be seen that I have provided astrain-relief structure which supplies all the advantages heretofore setforth.

Having thus described my invention, what I claim is:

1. A strain relief bushing of strong insulating material for holding anelectrical conductor in a suitable hole in a mounting member, comprisinga body portion having a flange only at one end to engage the mountingmember on one side thereof with a locking groove around its peripherylongitudinally adjacent said flange, the body having a longitudinalchannel therethrough with a single recess positioned below the channeland having walls at both ends of the body portion, the body having guidechannels positioned on opposite sides or said longitudinal channel, agrip block adapted to be positioned in said longitudinal channel andhaving a single downwardly extending portion with an end formation toengage an electrical conductor and also having slide portions forengaging said oppositely positioned channels, said grip block having onits outer peripheral surface a groove, one side of which is insubstantially the same plane as the inner edge of said body flange, theblock having a height such that when it is forced into said hole in themounting member with the body portion, it will be forced by the wall ofsaid hole into strong gripping engagement with a conductor located insaid longitudinal channel, both parts of the bushing having their endsopposite said flange tapering inwardly for the purpose described.

2. A strain relief bushing of strong insulating material for holding anelectrical conductor in a suitable hole in a mounting member, comprisinga body portion having a flange at one end only to engage the mountingmember on one side thereof with a locking groove adjacent said flange,the body only having a longitudinal channel therethrough with a singlerecess positioned below the channel, a grip block adapted to fit in saidchannel with means for preventing it shifting endwise in the channel,said block having a downwardly extending portion with an end for mationto engage an electrical cable, the block also having on its outersurface a groove, one side of which is in substantially the same planeas the inner edge of said body flange, the block having a height suchthat when it is forced into said hole in the mounting member with thebody portion, it will be forced by the wall of said hole into stronggripping engagement with a conductor located in said longitudinalchannel, both parts of the bushing having their ends opposite saidflange tapering inwardly for the purpose described.

3. A strain relief bushing of strong insulating material for holding anelectrical conductor in a suitable hole in a mounting member, comprisinga body portion having a flange at one end to engage the mounting memberon one side thereof with a locking groove adjacent said flange, thebushing having a longitudinal channel therethrough with a recesspositioned below the channel, a T-shaped grip block having thehorizontal part of the T of substantially the same length as said bodyportion and fitting in said channel, one end having a locking groove toreceive a surface on the mounting member while its opposite end istapered inwardly in a direction away from the groove to assist ininserting the bushing into the mounting member hole, the vertical partof the T extending toward said recess and having an end formation togrip a cable positioned within said channel, the dimensions of the Tbeing such as to cause the vertical part of the T to force the cable outof the plane of the bottom of the channel toward the bottom of saidrecess when the bushing is inserted into said suitable hole in themounting member.

4. A strain relief bushing of strong insulating material for holding anelectrical conductor in a suitable hole in a mounting member, comprisinga body portion having a flange at one end to en gage the mounting memberon one side thereof with a locking groove adjacent said flange, thebushing having a longitudinal channel therethrough with a recesspositioned below the channel, a T-shaped grip block having thehorizontal part of the 'l of substantially the same length as said bodyportion and fitting in said channel, with means for preventing itsshifting lengthwise in the channel, one end of this horizontal parthaving a locking groove therein for arcuate alignment with the lockinggroove in said body portion when the grip block is in assembledposition, the end of the grip block farthest from the locking groovebeing inwardly tapered in a direction away from the groove to assist ininserting the bushing into the mounting member, the vertical part of theT extending toward said recess and adapted to be forced by the wall ofthe mounting member hole onto a cable extending through the channel soas to deflect it into said recess.

5. A two-piece strain-relief bushing of suitable material for holding aconductor or cable in a suitable hole in a mounting member, both pieceshaving cooperative means for holding the pieces securely in the mountingmember hole when inserted therein, one piece having a longitudinalchannel therethrough and a single recess positioned below the plane ofthe bottom of the channel, the other piece having a part adapted to liewithin the channel with cooperative means on the two parts forpreventing longitudinally shifting of the two parts, said other piecehaving a downwardly extending portion positioned over said single recessand adapted to be forced by the wall of the mounting plate hole onto theconductor or cable to cause it to be deflected into the recess.

6. The combination of a mounting plate having a hole therein and astrain relief bushing of suitable insulating material to fit in saidhole, the bushing being in plural parts, and adapted to grip anelectrical conductor cable, one part having a. main channel longitudinalof its length,

the bottom wall of the channel being broken by a recess while theopposite side walls of the main channel have guide channels therein, theother part of the bushing having a projection the opposite edges ofwhich are adapted to slide in said guide channels when the two parts areforced toward each other by insertion of said parts into said holewhereby said projection will force the conductor or cable into saidrecess, each main part having a tapered end to assist in entering thebushing into the hole, both main parts having cooperative circular typegrooves to lock the parts to the mounting plate.

'7. A strain relief bushing of strong insulating material for holding anelectrical conductor in a suitable hole in a mounting member comprising,two parts of substantially the same length and having a peripherallocking groove positioned at one end to form a circular flange to engagethe mounting member on one side thereof, the opposite ends of said partsbeing inwardly tapered for assisting in the assembly of said parts intothe mounting member hole, at least one of said parts having alongitudinal channel therethrough with a, recess positioned below thechannel, the 25 other part carrying a projection of suitable lengthpositioned over said recess when the parts are in operative position andhaving an end formation to engage an electrical cable, the two partshaving a height such that they will be forced by the wall of the hole inthe mounting member toward each other whereby the said projection willforce the cable toward the button of said recess. FERDINAND KLUMPP, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,240,844 Gregur Sept. 25, 1917945,350 Tinsley Jan. 4, 1910 2,277,637 Eby Mar. 24, 1942 1,027,601Gressett May 28, 1912 FOREIGN PATENTS Number Country Date 412,712 GreatBritain July 5, 1934 550,035 France Dec. 5, 1922

